Aletaha M. MD

Labbafinejad Medical Center , Shahid Beheshti University

Extraocular muscle function

Muscle primary secondary Tertiary

Medial rectus Adduction -------------- ------------

Lateral rectus Abduction -------------- -------------

Inferior rectus Depression Excycloduction Adduction

Superior rectus Elevation Incycloduction Adduction

Inferior oblique

Excycloduction

Elevation Abduction

Superior oblique

Incycloduction

Depression Abduction

Internal carotid artery

Ophthalmic artery

Muscular artery

Lateral(superior)

Medial(inferior)

LRM – SRM –SOM- LPS-

MRM –IRM -IOM

EOM arteries

Fusion

Strabismus =Ocular deviation Tropia ,Phoria ,Intermittent tropia

Comitant , Incomitant

Primary, Secondary

Unilateral, Alternate

Esodeviation (esophoria, esotropia,intermittet esotropia)

Exodeviation (exophoria ,exotropia , intermittent exotropia)

Hypedeviation or hypodeviation

Synergists (Agonists)Cooperative muscles in an eye to produce a special function

AntagonistsOpposite acting muscles in an eye

YokeCooperative muscles in both eyes to produce

a special version

Relationship of EOMs:

Agonist Synergist Antagonist

Medial rectus SRM- IRM LR –SO- IOM

Lateral rectus SOM - IOM IRM –MRM -SRM

Superior rectus IOM -MRM IRM- SOM

Inferior rectus SOM -MRM SRM -IOM

Superior oblique IRM -LRM IOM -SRM

Inferior oblique SRM - LRM SOM -IRM

Synergist and antagonist muscles

Sherrington's law:

Contractional power of Agonist

muscles is equal to the

relaxational power of Antagonist

muscles.

Herring’ s law:

Equal innervations isinduced to yoke musclesFor each binocularmovement.

Hering ‘s law ,Yoke muscles

Versions

Vergence

History taking Age of onset of a deviation

Did its onset coincide with trauma or

illness

Is the deviation constant or intermittent

Is it present for distance ,near or both

Is it unilateral or alternating

Is the deviation associated with double

vision

Con…

Is it present only when the patient is inattentive or fatigued

Does one eye have a tendency to close when the patient is outside in bright sunlight

History of thyroid or neurologic disease

Earlier treatment :

Amblyopia therapy, Spectacles ,Miotics, Orthoptic therapy , Prior eye muscle surgery

Physical examComplete eye exam

Best visual acuity ,far or near E-chart – CSM methods

Full cyclo-refraction

Tests of ocular movement

Tests of ocular alignments Cover tests , corneal light reflex

Monocular cover test

Alternate cover test

Alternate prism cover test

Simultaneous alternate prism cover test

Light reflex

Amblyopia

Amblyopia is a unilateral or bilateral reduction of best corrected visual acuity

Nearly all amblyopic visual loss is

preventable or reversible with

timely detection and appropriate

intervention.

Amblyopia is caused by abnormal

visual experience early in life

Strabismus

Refractive error

Visual deprivation

Classification

Strabismic amblyopia

Most common

Anisometropic amblyopia

Unequal refractive error

Isometropic amblyopia

Deprivation amblyopia

Treatment

Eliminating any obstacle of

vision such as cataract

Correcting refractive error

Forcing use of the poorer eye

by limiting use of the better

eye

Acquired strabismusNew onset eye deviationRuled out neurologic problemTreatment

Management of underlying lesion Relieving diplopia Prevention of amblyopia Surgery

Sixth nerve palsyIncomitant esodeviation

Acquired palsy Diplopia ,head turn

Intracranial lesion(1/3) ,infectious or immunologic process ,head trauma , increased ICP

Patching , prism , injection of Botox, surgery

Fourth nerve palsyUnilateral bilateral

Congenital or acquired (closed head trauma , CNS vascular problem, DM, brain tumor)

Hyperdeviation , head turn , extorsion

Treatment : follow up,surgery

Third nerve palsy Children: Congenital(40-50%) ,

trauma , inflammatory ,neoplastic lesion..

Adult: intracranial aneurysm, DM , trauma , infection , tumor

Exodeviation ,hypodeviation , ptosis ,mydryasis

Follow up, Surgery

Myasthenia gravis

MG is a chronic disease of

neuromuscular transmission

Palsy of various extraocular muscles

The easy fatigability of the muscle

Any type of strabismus

MG must be considered in any patient with acquired ptosis or diplopia.

The muscles may be involved in only one eye

Pupillary abnormalities are uncommon

Characterized by remissions and exacerbations